It is known that the term “childbirth labor” refers to the complex of mechanical and dynamic phenomena which lead to the expulsion of the fetus and placenta and which, conventionally, is subdivided into three stages. The first stage, which relates to the dilatant period, that is, to the beginning of the labor up to the complete dilatation of the uterine cervix, is in turn subdivided into a “latent period”, characterized by a dilatation of 3–4 cm, and a following “active period” which leads to a complete 15 dilatation. The second stage, which relates to the expulsive period, goes from the complete dilatation to the delivery. The third stage, which relates to the discharge of the after-birth, ends up with the expulsion of the placenta.
It is also known that the deficiency, alteration or insufficient coordination of the uterine contractions may cause problems upon the expulsive stage, which is the delivery's most delicate one. In particular, it may happen that the uterus is not able to produce, with its contractions, a force of an intensity sufficient to conclude the delivery's expulsive stage (hypokinesia). It may happen, besides, that the expectant mother, in spite of the therapies commonly provided for treating such cases, is unable to produce a thrust—through a corresponding contraction of the abdominal press—adding up to the force generated by the uterine contraction. And, since a prolonged rest of the fetus in the delivery duct may seriously endanger the health condition thereof, a so-called Kristeller maneuver is generally performed by the health personnel, which consists in exerting, with an arm, a series of thrusts upon the bottom of the uterus, with the purpose of assisting the natural expulsive forces and speeding up the progression and disengagement of the fetus. However, this maneuver has risks inasmuch as it may cause the rupture of the uterus, the detachment of the placenta and acute fetal pains as well.
Also known in obstetrics is the use of the electromyograph (EMG) by which it is possible to register the electrical phenomena of the uterus' natural and involuntary contractions by deriving the relevant electrical potentials via electrodes applied on the patient's abdomen: an application software to be run on a PC provides for a graph of said electrical potentials versus time. However, the use of only an EMG does not provide any aid to the parturient's thrust and, moreover, the contraction graphs plot also other spurious signals such as spikes, tensions induced by the activation of other apparatuses and by neon glow lamps.
Also known in obstetrics is the use of the Pressure Labor Assister (PLA), with pressure sensors-controlled software, which utilizes the pressure increase inside an air chamber—formed within an abdominal band fixed around the patient's body—and which occurs as a consequence of the natural uterine contractions, to provide an automatic extra force, as an aid to the parturient, for the expulsion of the future baby.
On the other hand, this known device PLA does not provide a chart nor a record of the uterine contractions, and may also be a source of dangers, inasmuch as the possible overpressures on the pneumatic band, which are independent of the contractions but are due instead, for example, to more or less involuntary movements of the parturient, are always interpreted as a signal of uterine contraction and, in such case, it may occur that the consequent inflation of the abdominal pneumatic band will take place during a rest period, between one contraction and another, thereby dangerously reducing the inflow of blood to both the parturient and future baby.